This invention relates to a digital indicator which is simple in construction yet capable of displaying flat and easy to read large dotted figures clearly in daylight as well as at night.
Digital indicators are not widely used in various devices such as counters, meters, clocks and the like. This invention provides an improved segment type digital indicator wherein seven, eight or nine segments are used to form Arabic characters from "0" through "9".
For example, U.S. Pat. No. 3,683,523 to Boyles describes a 7-segment type digital indicator wherein a vertically movable shutter having horizontal segments and a horizontally movable shutter having vertical segments are mounted behind a front panel which is provided with seven straight-line slots in the form of the figure "8". With the Boyles device the numerals from "0" through "9" are formed from seven straight-line indicator segment slots in the front panel when the vertically and horizontally movable shutters are selectively moved relative to each other. This type of digital indicator has certain drawbacks in that illumination of the figures is almost impossible without an internal light source and the visibility of the displayed figures is poor when a strong outside light shines upon the front panel of the indicator. Another difficulty usually encountered with the prior art segment type digital indicators of the Boyles type is that incorrect figures are displayed on the front panel during the transition between the disappearance of a numeral and the appearance of the next numeral. For example, when the figure on display is changed from " 3" to "4", the numerals "7" and "9" appear in sequence before the figure "4" is finally displayed. Similarly, when the figure is changed from "4" to "5", the numerals "0", "8" and "6" sequentially appear on the front panel during the transition between the disappearance fo the figure "4" and the appearance of the intended figure "5". This latter deficiency is due to the fact that a number of opaque shutter bars on both the vertically movable shutter and the horizontally movable shutter form unnecessary combinations while both shutters are moved and is considered to be a detrimental defect inherent to the construction of the indicator.
Digital indicators having rotary cylinders which bear printed numerals on the circumferential surfaces thereof are also known in the art. The rotary cylinder type digital indicators have been widely used, for example, as mileage-meters for motor vehicles. However, with these rotary type indicators the displayed figures are small as compared to the bulky operating mechanism, and are difficult to read because they are printed on a curved surface.
Accordingly, it is an object of the present invention to provide a segment type digital indicator which will overcome the aforementioned difficulties and drawbacks of the prior-art digital indicators.
It is another object of the present invention to provide a digital indicator which is capable of displaying flat and easily readable dotted figures clearly in daylight as well as at night.
It is a further object of the present invention to provide a segment type digital indicator which can display digital figures with a sophisticated effect comparable to that of an expensive luminous diode digital display indicator such as is used for sophisticated computers.
It is a still further object of the present invention to provide a segment type digital indicator which is able to display figures precisely, with no display on the front panel during the transitional time period between disappearance of a numeral and appearance of the next intended numeral.
It is a further object of the present invention to provide a segment type digital indicator which is simple in construction, simple in operation, extremely low in operational noise, and reliable in operation.